Ink cartridge



July 25, 1967 A SONNTAG INK CARTRIDGE Filed Feb. 11, 1965 INVENTORCLEMENS A. SONNTAG United States Patent 3,332,400 INK CARTRIDGE ClemensA. Sonntag, .lanesville, Wis, assignor to The Parker Pen Company,.ianesville, Wis, a corporation of Wisconsin Filed Feb. 11, 1965, Ser.No. 431,802 3 Claims. (Cl. 12045.4)

The present invention generally relates to ink reservoir cartridges ofthe type used in fountain pens and it more particularly relates to athrow-away type of cartridge having a reserve chamber therein and meansfor indicating to the user when only a small predetermined amount of inkremains in the cartridge.

Because of the ease and convenience of use, fountain pens employingthrow-away ink cartridges have become popular in the last few years.When the ink supply becomes exhausted in this type of fountain pen, thespent cartridge is removed and replaced with a new ink filled cartridge.Such cartridges cannot conveniently be refilled with ink from inkbottles and the like and, therefore, when the ink in a cartridge hasbeen used up it is necessary for the user to have available anothercartridge in order to continue writing with the instrument. Moreover,since the ink cartridges for different types of pens are not normallyinterchangeable, a new cartridge may not readily be available at theparticular time that the ink supply runs out. This has proven to be onedisadvantage or drawback to the use of cartridge-type fountain pens.

Accordingly, it would be desirable to incorporate into the fountain penor cartridge, means for indicating to the user when the ink supply isnearly exhausted so that he may make the necessary provisions to have anew cartridge available when the cartridge being used becomes empty. Asis more fully described hereinafter, the present invention provides asimple, inexpensive and yet reliable means for indicating when only asmall, predetermined amount of ink remains in the cartridge.

A principal object of the present invention is, therefore, to provide anew and improved ink reservoir for use in fountain pens and similarwriting instruments.

Another object of the present invention is to provide a new and improvedthrow-away type of ink cartridge reservoir.

Still another object of the invention is to provide a new and improvedink cartridge having means for indicating when only a predeterminedamount of ink remains therein.

A further object of the present invention is to provide a new andimproved ink cartridge incorporating therein a reserve chamber forholding a predetermined quantity of ink until the main chamber hasbecome exhausted and the user transfers the ink from the reserve chamberto the main chamber.

Briefly, the above and further objects are realized in accordance withthe present invention by providing near the rear end of a vacuum typeink cartridge a restriction having a cross-sectional shape and size suchthat the surface tension of the ink across such restricted area issufficient to hold a predetermined quantity of ink rearwardly of suchrestriction against the force of gravity and also against the forces ofmomentum normally encountered during use and transportation of thefountain pen. The surface tension of the ink across the restriction is,however, sufliciently small such that the meniscus may be broken to feedthe ink in the reserve chamber to the main reservoir chamber by sharplytapping the front end of the nib of the pen against a hard surface or bya lateral tapping of the rear end of the cartridge. When the meniscus isthus broken, the ink runs out of the reserve chamber down into the mainchamber thereby providing an additional quantity of ink which is of asmall predetermined amount to enable the writer to use the pen for asubstantial length of time. He will, however, be aware that the ink inthe pen is about to become exhausted and, therefore, a new cartridgeshould be available to replace the spent one.

Further objects and advantages and a better understanding of the presentinvention may be had by reference to the following detailed descriptiontaken in connection with the accompanying drawing, in which:

FIGURE 1 is a longitudinally sectioned view of a throw-away type of inkreservoir cartridge embodying the present invention, and

FIGURE 2 is a cross-sectional view taken along the line 2-2 of FIG. 1,assuming the entire reservoir to be shown in FIG. 1.

Referring now to the drawing, there is shown a throwaway type of inkcartridge 10 comprising a generally tubular shell 12 which may be moldedof a suitable plastic such, for example, as polyethylene, and a plug 13which has a tubular portion 14 fitted into one end of the shell 12 andsealed thereto by any suitable means as, for example, in a spinningoperation. The plug 13 further includes a generally annular flange 15which abuts against the marginal, annular end 16 of the shell 12 tofacilitate assembly of the cartridge 10 and to insure a hermeticallytight seal between the plug 13 and the shell 12. An integral wall 17 isprovided within the plug 13 to hold ink in the cartridge 1t) prior toits insertion in an associated fountain pen. When the cartridge isplaced in an associated fountain pen, the wall 17 is pierced orotherwise partially severed from the plug and shifted to one sidethereby to permit the passage of ink through the plug 13 and into thefeed mechanism of the pen. A fountain pen which is suitable for use withthe cartridge 10 is described in Patent No. 3,134,362 to Homer T. Green.The shell 12 has an outer envelope formed to closely follow the contourof the barrel of the pen in which it is adapted to be used, andtherefore the shell 12 tapers toward its upper or right-hand end asviewed in FIG. 1.

The right-hand or upper end of the cartridge shell 12 is sealed off bymeans of an integral end portion 20 thereby to completely seal therearward or upper end of the cartridge from the atmosphere.

The cartridge 10 is designed for use with liquid inks Which ordinarilyhave a surface tension of the order of 45 to 60 dynes per centimeter.Moreover, the shell 12 is preferably formed of :a relatively rigid andinexpensive material such, for example, as polyethylene. Linearpolyethylene has been found to be particularly suitable for such acartridge and is sufliciently nonwettable by conventional writing typefluid inks to support varying quantities of ink in the closed end of thechamber. In order to prevent such an occurrence, two pairs oflongitudinally extending ribs 21, 22 and 23, 24 extend from a location ashort distance rearwardly of the plug 13 to an annular flange 26provided near but spaced from the rear end 20 of the cartridge. The ribs21-24 and the flange 26 are integral with the shell 12 and arepreferably molded when the shell 12 is formed. The ribs 21 and 22 aresufficiently close together that the cross-sectional area of the channelformed between the ribs is of capillary .di' mension thereby to providea capillary passage from the location of the flange 26 to a locationnear the forward end of the cartridge 10. A similar capillary assage isprovided between the ribs 23 and 24. The ribs 21-24 thus prevent theformation of a meniscus forwardly of the flange 26 by draining the inkfrom the locations adjacent the rearward end of the ribs 21-24.

Rearwardly of the flange 26 there is thus defined a chamber 28 which isgenerally cylindrical in shape and which is separated from the remainderof the cartridge chamber by the flange 26. The chamber 28 provides areserve chamber in which a reserve quantity of ink is retained by themeniscus which forms across the restricted area defined by the inneredge of the flange 26. In the illustrated embodiment of the invention,the flange 26 is annular and defines a circular area of restrictedcross-section between the auxiliary chamber 28 and the remainder or mainportion of the cartridge chamber which is identified by the numeral 29.The chamber 29 is thus the main ink supply chamber and the ink containedtherein will be exhausted even though the reserve chamber 28 may remainfilled with ink.

In order to prevent the ink in the reserve chamber 28 from freelyflowing into the main chamber during use, the restricted area defined bythe flange 26 is chosen such that the surface tension of the meniscusformed by the ink across such area is sufficiently strong to hold thereserve chamber 28 filled with ink even though the cartridge is heldupright and is subjected to the occasional jarring and bumping which awriting instrument normally encounters. On the other hand, therestricted area formed by the flange 26 is sufficiently large so thatthe meniscus can be broken by sharply tapping the front end of thewriting instrument against a hard surface such, for example, as a normalwriting surface. For aqueous types of ink, it has been determined that acircular restricted area having a diameter of approximately 0.132 inchhas the desired characteristics when used with linear polyethylene,

Another factor which must be considered in determining the size of therestriction is the adapt-ability of the cartridge to eflicient moldingtechniques. By employing a flexible plastic for the cartridge, theflange is sufliciently flexible to permit facile withdrawal of a onepiece core pin after the cartridge is molded.

By providing the flange 26 and the associated restricted area at apredetermined location in the cartridge, there is provided a reservechamber 28 of predetermined size which will remain filled With inkduring normal use of the pen. Therefore, when a person using a pen findsthat it runs dry for the first time, he may merely tap the nib of thepen against the surface on which he is writing and will thereby breakthe meniscus formed across the restricted area at the location of theflange 26 whereby the ink from the reserve chamber 28 flows into themain chamber 29 and thence to the feed system of the pen. A small supplyof ink such, for example, as 0.1 cc. has been found to provide anadequate reserve supply so that by the time such reserve is used up thewriter can have another cartridge available.

Throughout this specification and claims the term capillary dimension isused to define a dimension which is sufficiently small when used with aparticular ink and cartridge material to result in a sufiicientcapillary force being exerted on the ink to transfer it along saiddimension.

While the present invention has been described in connection with aparticular embodiment thereof, it Will be understood by those skilled inthe art that many changes and modifications may be made withoutdeparting from the true spirit and scope of the invention. Therefore, itis intended by the appended claims to cover all such changes andmodifications as come within the true spirit and scope of thisinvention.

What is claimed is:

1. In an ink cartridge,

a rigid unitary, generally tubular plastic member closed at one end anddefining a chamber therein, and an integral annular flange extendinginwardly from the inner Wall of said member to define a restrictedpassageway of greater than capillary cross section connecting theadjacent portions of said chamber,

said flange being positioned nearer to said one end than to the otherend of said member,

said passageway being of such cross-sectional area that,

in normal usage of said pen, surface tension retains ink in one portionof said chamber, and that said surface tension is broken byintentionally jarring said pen.

2. The invention set forth in claim 1 comprising means defining acapillary groove extending from said flange into proximity with saidother end of said member.

3. An ink reservoir for insertion into a fountain pen embodying main andreserve ink supply chambers, Wherein ink is transferrable from saidreserve chamber to said main chamber Without removing said reservoirfrom said pen or opening said pen, the ink reservoir comprising:

a unitary, generally tubular and relatively rigid plastic member closedat one end,

an integral annular flange extending inwardly from the inner wall ofsaid member and defining main and reserve ink supply chambers therein,said flange defining a restricted passageway between said chambers,

said passageway being of such cross-sectional area that,

in normal usage of said pen, surface tension retains ink in said reservesupply chamber, and that said surface tension is broken by intentionallyjarring said pen, and

means defining a capillary groove extending from said -flangesubstantially the length of said main supply chamber, said annularflange extending farther inwardly from the inner wall of said memberthan do said means defining said groove.

References Cited UNITED STATES PATENTS 2,870,742 1/ 1959 Hackmeyer 45.43,167,056 1/1965 Bross 12042.16 3,167,057 1/1965 Bross 120-42163,237,606 3/1966 Sonntag 120-454 FOREIGN PATENTS 969,130 9/ 1964 GreatBritain.

LAWRENCE CHARLES, Primary Examiner.

1. IN AN INK CARTRIDE, A RIGID UNITARY, GENERALLY TUBULAR PLASTIC MEMBERCLOSED AT ONE END AND DEFINING A CHAMBER THEREIN, AND AN INTEGRALANNULAR FLANGE EXTENDING INWARDLY FROM THE INNER WALL OF SAID MEMBER TODEFINE A RESTRICTED PASSAGEWAY OF GREATER THAN CAPILLARY CROSS SECTIONCONNECTING THE ADJACENT PORTIONS OF SAID CHAMBER, SAID FLANGE BEINGPOSITIONED NEARER TO SAID ONE END THAN TO THE OTHER END OF SAID MEMBER,SAID PASSAGEWAY BEING OF SUCH CROSS-SECTIONAL AREA THAT, IN NORMAL USAGEOF SAID PEN, SURFACE TENSION RETAINS INK IN ONE PORTION OF SAID CHAMBER,AND THAT SAID SURFACE TENSION IS BROKEN BY INTENTIONALLY JARRING SAIDPEN.